The present invention relates to a data storage device, and more particularly to a data storage device configuration suitable for a load/unload type hard disk drive.
Various devices using optical disks, magnetic tapes, or other medium are known as a data storage device. Among others, a hard disk drive (HDD) is now widely used as a storage device for use with a computer and counted as an essential storage device for a present-day computer system. Thanks to its excellent characteristics, the hard disk drive has found an increasingly wide range of applications, including not only a computer system but also a motion picture recorder/player, a car navigation system, and a removable memory for use with a digital camera.
FIG. 12 is a perspective view illustrating the configuration of a conventional hard disk drive 900. As indicated in the figure, the conventional hard disk drive 900 comprises a base 902, a magnetic disk 901 for data recording, a suspension 910 whose leading end supports a head 905, an actuator 906 that includes the suspension 910 and an arm 911, and a ramp 915 for unloading the head 905.
The head 905 has a head element section, which is a thin-film element, and a slider. The head element section is mounted on a surface of the slider. The head element section has a write element section and a read element section. The write element section converts an electrical signal to a magnetic field in accordance with write data for a magnetic disk. The read element section converts a magnetic field generated from the magnetic disk to an electrical signal. Typically, the write element section and read element section are integrated as a single thin-film element.
When driven by a VCM (Voice Coil Motor) 909, the actuator 906 swings on a swing shaft 907 to move the head 905 to a desired position over the magnetic disk 901. This allows the head 905 to access a desired track, which is formed on the magnetic disk 901, and perform a data read/data write process. Power supply to the actuator 906 and signal exchange with the head 905 are performed via an FPC (Flexible Printed Circuit) 904, which is fastened to the arm 911.
This conventional hard disk drive 900 is a load/unload type hard disk drive so that the ramp 915 is positioned close to the outermost end of the magnetic disk 901. When the magnetic disk 901 stops rotating, the head 905 will be attracted to a surface of the magnetic disk 901. Therefore, when the magnetic disk 901 is about to stop rotating, the actuator 906 unloads the head 905 from a recording surface of the magnetic disk 901 to the ramp 915.
The suspension 910 is provided with a tab 916 at its leading end. When the tab 916 is led toward the ramp 915, the head 905 is unloaded as it moves from an area above the surface of the magnetic disk 901 to the outside. On the contrary, when the tab 916 moves away from the ramp 915, the head 905 is loaded as it moves from the outside of the magnetic disk 901 to an area above the surface of the magnetic disk 901. When the head 905 is about to become unloaded, the tab 916 needs to come into contact with the ramp 915 to move the head 905 away from the magnetic disk 901 while the head 905 is positioned over the magnetic disk 901. In the conventional hard disk drive 900, therefore, the magnetic disk 901 overlaps the ramp 915 and the actuator 906 in an unloading position.
FIG. 13 is a side view illustrating a load beam 940, which is at a leading end of the suspension 910 for use with the conventional hard disk drive 900. It shows a state of the load beam 940 that prevails when the head 905 is positioned over the magnetic disk 901.
As indicated in the figure, the head 905 is single-point-supported by a dimple 960 that is provided in the load beam 940, and flying at a predetermined height above the surface of the magnetic disk 901. The tab 916 is extended from the leading end of the load beam 940 and bent away from the magnetic disk 901. In other words, the positional relationship between the magnetic disk 901 and tab 916 is such that the tab 916 is formed and positioned higher than a head support section 940a of the load beam 940.
FIG. 14 is a cross-sectional view illustrating the ramp 915 used in the conventional hard disk drive 900. The figure shows the height of the tab 916 and the height of the ramp 915. In this document, the term “height” refers to the vertical distance from the recording surface of the magnetic disk.
As described earlier, the ramp 915 overlaps the magnetic disk 901. As indicated in the figure, the ramp 915 has a protrusion 915a, which protrudes and overlaps a peripheral surface of the magnetic disk 901.
The height of the ramp 915 is equal to A+H3+H4. The height A is the vertical distance between the surface of the magnetic disk 901 and the tab 916 that prevails when the head 905 is positioned over the magnetic disk 901. It is the height at which the tab 916 first comes into contact with the ramp 915 for unloading purposes. The height H3 is a mechanical error. It is a relative height error (3σ) between the ramp 915 and tab 916. The height H4 is a lift amount that is necessary for lifting the tab 916 to move the head 905 away from the surface of the magnetic disk 901.
Since the conventional ramp 915 needs to overlap the magnetic disk 901, it is necessary that the height A be greater than H1+H2+H3. The height H1 is the vertical distance between the surface of the magnetic disk 901 and the surface, of the protrusion 915a, opposite the magnetic disk 901. The height H1 is a margin for preventing the magnetic disk 901 from coming into contact with the ramp 915. It includes mechanical errors of the magnetic disk 901 and ramp 915. The height H2 is the height of a curved leading end surface (R) of the protrusion 915a. When the radius of the curved leading end surface is r and the inclination of the surface of the protrusion 915a is θ, H2=r(cos θ). Since the ramp 915 is made of resin, the surface of the leading end of the protrusion 915 is curved.
If, for instance, the height A is less than H1, the tab 916 is positioned between the protrusion 915a and magnetic disk 901 at the time of unloading so that loading cannot be accomplished any longer. If the height A is less than H1+H2, unloading cannot be accomplished because the tab 916 is caught by the curved leading end surface of the protrusion 915a at the time of unloading.
Conventional load/unload type hard disk drives are disclosed by Patent Documents 1 to 4: (1) Japanese Patent Laid-open No. 2001-291349; (2) Japanese Patent Laid-open No. 2004-152360; (3) Japanese Patent Laid-open No. 2005-11511; and (4) U.S. Pat. No. 6,778,360.